JPH11266505A - Driving control method of electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a constant damping operation on a flat road, and at the same time reduce frequent braking on a sharp down slope by selecting a larger value out of a predetermined damping torque and a damping torque that is obtained by calculation as a regeneration damping torque in regeneration damping on acceleration off. SOLUTION: When an accelerator 2 is turned off, while an electric vehicle is being driven, the upper-limit speed on accelerator off driving being preset by a control part 5 is compared with a current driving speed, and a first damping torque required for setting the driving speed to the upper-limit speed is obtained by calculation. Then, a second damping torque that is a predetermined constant value is compared with the first damping torque and the electric motor is subjected to regeneration damping with a larger damping torque. Therefore, regeneration damping is made mainly with a second damping torque with a constant width on accelerator off driving on a flat road. Furthermore, speed can be decelerated with a damping torque for preventing the upper-limit speed from being exceeded on accelerator-off driving, in a situation where acceleration is enabled even on a sharp down slope or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a travel control method which can be suitably used for an electric vehicle such as a battery-powered forklift.

[0002]

2. Description of the Related Art In an electric vehicle, for example, a battery-powered forklift, traveling starts when an accelerator is turned on. However, when the accelerator is turned off during traveling, the vehicle normally enters a coasting state. The running speed gradually decreases. Further, when it is desired to reduce the traveling speed of the forklift quickly, the driver operates the brake.

In recent years, there has been a strong demand for improved driving operability even in such electric vehicles. In particular, when the accelerator is turned off while driving, if a braking feeling like an engine brake of an internal combustion engine automobile is obtained, frequent braking operations are reduced, especially on a long downhill, and the driving effort of the driver is reduced. Can be greatly reduced, which is very convenient.

There are several methods for obtaining such a braking feeling. As one of the methods, for example, a method of storing a traveling speed when an accelerator is turned off and applying an electric brake to a traveling motor of the forklift so that the forklift does not exceed this speed can be considered. However, in this method, for example, when traveling on a flat road, even if the accelerator is turned off, the braking effect can be obtained only with the same small deceleration width as normal coasting traveling, and when it is desired to decelerate quickly, Also, the brake operation is required, and the driving labor cannot be reduced.

As another method, when the accelerator is turned off during traveling, a method of electrically braking the electric motor with a predetermined constant braking torque can be considered.
However, in this method, since the braking torque is determined to be a constant value, there is a problem that a sufficient braking effect cannot be obtained, such as when the vehicle is accelerated by gravity on a steep downhill.

Further, on a downhill or the like, if the brake is released after the forklift is temporarily stopped after the accelerator is turned off, the traveling speed may increase again due to gravity. In such a case, it is very convenient if the electric braking works so that the vehicle can go downhill at a relatively small constant traveling speed.

[0007] The present invention has been devised in view of the above-mentioned problems, and according to the first to fifth aspects of the present invention, when the accelerator is turned off while the electric vehicle is traveling, the constant speed exceeding the coasting traveling is maintained. It is an object of the present invention to provide a driving control method for an electric vehicle that can achieve a braking action of the vehicle, suppress acceleration running even on a steep downhill, reduce frequent braking operations, and greatly reduce driving labor. .

According to the present invention, when the accelerator is turned off and the running speed of the electric vehicle increases to a running speed at which regenerative braking can be performed after the running speed has decreased, the lowest running speed that can be controlled by regenerative braking. An object of the present invention is to provide a traveling control method for an electric vehicle that can suppress accelerated traveling even on a steep downhill or the like by reducing braking, and can reduce frequent braking operations to greatly reduce driving labor.

[0009]

According to a first aspect of the present invention, there is provided a traveling electric motor which is supplied with electric power from a battery and is driven in accordance with an operation amount of an accelerator, and regenerating the electric motor. A traveling circuit for switching to a braking state;
A traveling control method for an electric vehicle, comprising: speed detection means capable of detecting a traveling speed of the electric vehicle, wherein when the electric vehicle is traveling and the accelerator is turned off, a preset accelerator-off traveling The upper limit speed of the vehicle is compared with the current travel speed, and the first speed necessary for setting the travel speed to the upper limit speed is determined.
And a second braking torque T2, which is a predetermined constant value.
And a first braking torque T1 obtained by the calculation, and performing a regenerative braking process for regeneratively braking the electric motor with a larger braking torque.

The electric vehicle according to claim 1, wherein the upper limit speed is set by reading a traveling speed when the accelerator is turned off from the speed detecting means. Is a traveling control method.

According to a third aspect of the present invention, in the electric vehicle regenerative control method according to the first aspect, the upper limit speed is set by an adjuster provided near a driver's seat of the electric vehicle. is there.

According to a fourth aspect of the present invention, the first braking torque T1 is such that the current running speed of the electric vehicle is Vr, the acceleration of the electric vehicle is α, the upper limit speed is Vu, and an appropriate gain is G1, G2 and I are integral operation parameters, Ib is a previously calculated value of the integral operation parameter, P is a proportional operation parameter, P
4. The running of an electric vehicle according to claim 1, wherein when b is the previous calculated value of the proportional operation parameter, the value is obtained by an operation including a proportional integral operation substantially equivalent to the following equation. It is a control method. T1 = I + P where I = Ib + (Vr−Vu) × G1 P = Pb + α × G2, where T1 is% of the rated torque of the electric motor,
0 ≦ T1 ≦ 100

According to a fifth aspect of the present invention, the second braking torque T2 is set by an adjuster provided near a driver's seat of the electric vehicle.
It is a regeneration control method of the electric vehicle according to any one of the above.

According to a sixth aspect of the present invention, there is provided a traveling electric motor which is supplied with electric power from a battery and is driven in accordance with an operation amount of an accelerator, a traveling circuit for switching the electric motor to a regenerative braking state, A travel control method for an electric vehicle, comprising: a speed detection unit capable of detecting a travel speed of the vehicle, wherein the accelerator is turned off, and a travel speed at which regenerative braking is possible after the travel speed of the electric vehicle is reduced. When the vehicle speed rises, a process of setting a minimum speed of the electric vehicle that can be controlled by regenerative braking, and comparing the minimum speed with the current travel speed, a process required to set the travel speed to the minimum speed is performed. A third braking torque calculation process for calculating the third braking torque T3 and a regenerative braking process for regeneratively braking the electric motor with the third braking torque T3 are performed.

[0015]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 illustrates a traveling circuit C of a battery-powered forklift as an electric vehicle. In FIG. 1, a traveling circuit C includes a battery BA, a DC motor 4 as an electric motor for traveling in this example, and a DC motor 4 provided between the DC motor 4 and the battery BA and connected to the DC motor 4 by conduction. And a traveling switching unit CH1 such as an FET that can supply power from the battery BA.

The DC motor 4 includes a regenerative contactor MG having normally closed contacts, an armature 4A connected to the positive side of the battery BA via a fuse H, etc., a forward contactor MF as a traveling contactor, and a reverse contactor MR. And a field coil 4B interposed therebetween, and a motor shaft (not shown) is linked to driving wheels.

The forward contactor MF and the reverse contactor MR open and close the contact f or r in response to a forward or backward instruction of a direction indicator (shown in FIG. 2) provided in a driver's seat or the like during normal traveling. The excitation polarity of the field coil 4B can be switched. Forward and reverse contactors M
F and MR are connected to the minus side of the battery BA via the traveling switching unit CH1.

A first line L1 connecting the contactor MG for regeneration and the battery BA, and a second line L2 connecting the armature 4A to the forward and backward contactors MF, MR are connected to a regeneration control for regeneration. A third line L in which a resistor R and a pre-excitation switching unit CH2 are arranged in series
3 and via an amateur plugging diode D2.

Further, a fourth line L4 connecting the forward / backward contactors MF, MR and the traveling switching unit CH1 is connected to the first line L1 via a first regenerative diode D1. I have. The fifth line L5 connecting the traveling switching unit CH1 and the negative terminal of the battery BA and the first line L1 are
It is connected via a second regenerative diode D3.

The second line L2 includes an armature current Ia and a field current If of the DC motor 4.
Are respectively provided.

FIG. 2 is a control block diagram of the forklift of this embodiment. In this example, each of the accelerator 2, the direction indicator 6, the adjuster 3 that can freely set a second braking torque T2 described later, the current detectors STa and STf, and the speed detector 11 that detects the traveling speed of the forklift. The signal is input to the input interface I of the control unit 5.

The accelerator 2 is composed of, for example, an operation lever 2a that is tilted by a driver and a potentiometer 9 that outputs a speed command value corresponding to the amount of tilt of the operation lever 2a. May be used as a pedal. Further, the direction indicator 6 is exemplified by limit switches 6a and 6b which are operated by a substantially fan-shaped dog 2b which is tilted integrally with the operation lever 2a and which outputs a forward or backward signal.

The adjusting device 3 includes a display device provided in, for example, a driver's seat of a forklift and an adjusting switch (both are not shown), and adjusts while checking the second braking torque T2. Examples are shown. The second braking torque T2 is used, for example, to decelerate the forklift with a constant braking torque when the accelerator 2 is turned off. If it is too large, the braking shock is large, and if it is too small, the conventional coasting is performed. Since there is no great difference from deceleration due to running, it is preferable to determine the value according to the specific forklift from such a viewpoint. For example, the value is larger than 0% of the rated torque of the DC motor 4 and 50%.
% Or less, more preferably 10 to 30% of the rated torque
It is preferred that

The control section 5 includes a readable / writable RAM as a working memory, and a ROM in which processing procedures such as programs are stored in advance. The ROM is an EPROM (Erasable and Programmable Read).
-Only Memory) or the like to adjust the adjuster 3
The modified second braking torque T2 can be stored even after the key switch of the forklift is turned off.

In the embodiment configured as described above, for example, a processing procedure as shown in FIG. 3 is performed.

In this embodiment, when the accelerator 2 is turned on (Y in step S1), a regeneration flag described later is cleared (step S2), a regeneration contactor closing process for closing the regeneration contactor MG (step S3), and forward movement And a traveling contactor power running switching process (step S4) for switching the contact points of the reverse contactors MF and MR to the direction indicated by the direction indicator 6 to conduct the traveling switching unit CH1 according to the tilt amount of the accelerator 2. A powering operation process is performed by flowing a predetermined current from the battery BA to the DC motor 4 (step S5).

When the accelerator 2 is turned off during running (N in step S1), the control unit 5 checks the speed information input from the speed detecting means 11 and determines whether the running speed is sufficient for regenerative braking. Is determined (step S6). And
If the speed is such that regenerative braking is possible (Y in step S6), it is determined whether or not the speed is on with reference to the value of the regenerative flag (step S7).

Here, the "regeneration flag" is a flag for storing that the accelerator 2 has been turned off, and that the traveling speed of the electric vehicle has decreased and then increased to a traveling speed at which regenerative braking is possible. It is stored at a predetermined address on the RAM. In the present embodiment, the accelerator is turned off as a condition for turning on the regeneration flag (N in step S1).
It is determined that the running speed is lower than the regenerative braking possible speed (N in step S6), and the regenerative flag is turned on until the accelerator is turned on again.

When the regenerative flag is off (N in step S7), the current traveling speed of the forklift is set (stored) in the RAM as the upper limit speed when the accelerator is off (step S16). The second braking torque T2 set in advance is read from the ROM and set (stored) in the RAM (step S17).

Next, the control unit 5 opens the regenerative contactor MG (step S18), and
A running contactor regeneration switching process for switching F and MR to an excitation direction opposite to the current rotation direction of the amateur 4A is performed (step S19).

Thereafter, the present traveling speed of the forklift is compared with the upper limit speed when the accelerator is off, and the first braking torque T1 which is a braking torque necessary for setting the speed to the upper limit traveling speed. Is performed (step S2).
0).

In the present embodiment, the first braking torque T1 is determined by setting the current traveling speed of the forklift to Vr,
The running acceleration is α, the upper limit speed is Vu, the appropriate gains are G1, G2, and I are the integral operation parameters, Ib is the previous calculated value of the integral operation parameter, P is the proportional operation parameter, and P is the proportional operation parameter.
When b is the previous calculated value of the proportional operation parameter, a value obtained by an operation including a proportional integral operation substantially equivalent to the following equation (hereinafter, such control is sometimes referred to as “PI control”) is exemplified. doing. T1 = I + P where I = Ib + (Vr−Vu) × G1 P = Pb + α × G2, where T1 is% of the rated torque of the electric motor,
0 ≦ T1 ≦ 100

Therefore, the first braking torque T1 increases as the difference between the current running speed of the forklift Vr and the upper limit speed increases and as the running acceleration α of the forklift increases. Excellent value is obtained. The running acceleration of the forklift can be easily derived by performing a Kochi process on the speed information.

When the first braking torque T1 is obtained by calculation, the second braking torque T2, which is a predetermined constant value, and the first braking torque T1
(Step S21), and performs regenerative braking processing for regenerative braking the DC motor 4 with the larger braking torque.

That is, when the first braking torque T1 is equal to or larger than the second braking torque T2 (Y in step S21), the regenerative braking process is performed using the first braking torque T1 (step S22). When the second braking torque T2 is larger (N in step S11), the regenerative braking process is performed using the second braking torque T2 (step S23).

As described above, in this embodiment, the regenerative braking is performed when the accelerator of the forklift is turned off, but the regenerative braking torque at that time is the second braking torque T2 which is a predetermined constant value. And the first braking torque T1 obtained by the above calculation, the larger value is adopted. Therefore, during accelerator-off traveling on a flat road, the regenerative braking is mainly performed with the second braking torque having a constant width. In a situation where acceleration can be applied, such as a steep downhill, where acceleration is applied, the vehicle can be decelerated with the first braking torque that does not exceed the upper limit speed during accelerator-off traveling.

For this reason, when the accelerator is turned off while the electric vehicle is running, a constant braking action exceeding that of coasting can be obtained on a flat road, and frequent braking operation can be reduced even on a steep downhill. Labor can be greatly reduced.

In the regenerative braking process, a pre-excitation process is performed in which the pre-excitation switching unit CH2 is turned on to apply a weak current to the field coil 4B whose excitation polarity is switched in the regenerative braking direction. When an electromotive force V is generated in the armature 4A that continues to rotate in the direction, the current I1 starts to flow (FIG. 4).

When the electromotive force V increases to a certain voltage, in addition to the current I1, the current I is passed through the second regenerating diode D3 toward the first line L1.
2 flows. When this current I2 increases to a certain value,
The conduction of the pre-excitation switching unit CH2 is forcibly cut off.

When the pre-excitation switching unit CH2 is turned off, the current from the battery BA is cut off. However, the current I2 is supplied to the second regenerative diode D3, the armature 4A, the current detectors STa and STf, and the forward contactor. MF, field coil 4B, reverse contactor MR, traveling switching unit CH1, second regeneration diode D
It still flows in the direction of 3.

In this state, the traveling switching unit CH1
5, the second regeneration diode D3, the armature 4A, the current detectors STa and STf, the forward contactor MF, the field coil 4B, the reverse contactor MR, and the first regeneration, as indicated by arrows in FIG. The current I3 flows in the direction of the diode D1, the first line L1, the + side of the battery BA, the − side of the battery BA, the fifth line L5, and the second regenerative diode D3.

By regenerating the electric power generated by the DC motor 4 to the battery BA in this manner, the battery BA is charged, which contributes to an increase in the operating time per charge. Is controlled by the regenerative braking torque T based on

Here, in the case of a DC motor, the regenerative braking torque changes in proportion to the square of the regenerative current. Therefore, by adjusting this regenerative current value, the DC motor 4 is braked with the determined braking torque. Can. The adjustment of the regenerative current can be performed by turning on / off the switching unit for traveling CH1 at an appropriate conductivity.

Next, for example, on a downhill, if the brake is released after the forklift is temporarily stopped and the accelerator is off, the traveling speed may increase again due to gravity. In this case, the regenerative flag is set to ON (stored) through the processing of N in step S1 and N in step S6 (step S1).
5).

Then, when the forklift gradually accelerates due to the downward slope and rises to a speed at which regenerative braking can be performed (Y in step S6), the value of the regenerative flag is checked.
If it is turned on (Y in step S7), the minimum speed of the forklift that can be controlled by regenerative braking is set, and RA
A process of setting (storing) in M is performed (step S8).
The minimum speed at which such regenerative braking can be performed is 3 km /
h.

Next, a third braking torque calculation process for calculating a third braking torque T3 necessary for setting the traveling speed of the forklift at the minimum speed is performed (step S1).
1) A regenerative braking process for regeneratively braking the DC motor 4 with the third braking torque T3 is performed (step S1).
2). The third braking torque T3 can be obtained by substantially the same method as the above-mentioned PI control calculation equation. At this time, the controllable minimum speed of the forklift may be substituted for the upper limit speed Vu. .

As described above, in the present embodiment, when the accelerator 2 is turned off and the traveling speed of the forklift is increased to a traveling speed at which regenerative braking can be performed after the traveling speed of the forklift has decreased, the forklift can be controlled by the regenerative braking. Electrical braking can be applied to run at speed. Therefore, on a downhill, if the brake is released after the forklift has been stopped and the accelerator is off, the traveling speed may increase again due to gravity. This is preferable in that the vehicle can descend on a downhill at a relatively low constant traveling speed, the braking feeling is good, and the frequent brake operation can be reduced.

When the accelerator 2 is operated in the middle (Y in step S13 or S24), the regenerative braking can be stopped to switch to the power running operation (step S1).
And Y). Further, when the regenerative current stops flowing even when the regenerative braking is performed (N in step S14 or S24), it is determined that the traveling speed has sufficiently decreased, and the regenerative braking is terminated to perform coasting.

Although the embodiment of the present invention has been described by taking a battery type forklift as an example, it goes without saying that the present invention can be applied to an electric vehicle and other various electric vehicles. In addition, the upper limit speed of the electric vehicle when the vehicle is traveling with the accelerator off is illustrated as being set to the traveling speed when the accelerator is turned off. The determination can also be suitably implemented. Further, various motors other than the DC motor can be adopted as the electric motor.

[0050]

As described above, according to the first aspect of the present invention,
When the electric vehicle is running off the accelerator, for example, on a flat road, a constant braking action that exceeds that of coasting can be obtained, and frequent braking operation can be reduced even on a steep downhill, and the driving labor can be greatly reduced. Become.

According to the second aspect of the present invention, since the upper limit speed of the electric vehicle when the accelerator is off is set to the running speed when the accelerator is turned off, the accelerator is turned off even on a steep downhill. Accelerated running exceeding the speed can be suppressed.

According to the third aspect of the present invention, the upper limit speed is set by the adjuster provided near the driver's seat of the electric vehicle, so that the driver can easily perform a desired driving or braking feeling according to the driver. realizable.

According to the fifth aspect of the present invention, the second braking torque is set by an adjuster provided in the vicinity of the driver's seat of the electric vehicle. It is easy to adjust and good driving feeling is obtained.

According to the present invention, when the accelerator is turned off and the running speed of the forklift is increased to a running speed at which regenerative braking is possible after the running speed is reduced, the forklift is driven at the minimum speed controllable by the regenerative braking. It is possible to travel, and on a downhill, etc., it is possible to descend on a downhill at a relatively small constant traveling speed without performing a brake operation, and the braking feeling becomes good,
In addition, the driving labor can be reduced.

[Brief description of the drawings]

FIG. 1 is a traveling circuit diagram of a battery-powered forklift according to an embodiment.

FIG. 2 is a block diagram of the embodiment.

FIG. 3 is a flowchart illustrating a processing procedure of a control unit;

FIG. 4 is a traveling circuit diagram of a battery-powered forklift illustrating regeneration.

FIG. 5 is a traveling circuit diagram of a battery-powered forklift illustrating regeneration.

[Explanation of symbols]

 2 Accelerator 3 Adjuster 4 DC motor 5 Control unit 6 Direction indicator 11 Speed detecting means CH1 Running switching unit CH2 Pre-excitation switching unit

Claims (6)

[Claims] An electric motor for traveling, which is supplied with electric power from a battery and is driven in accordance with an operation amount of an accelerator, a traveling circuit for switching the electric motor to a regenerative braking state,
A traveling control method for an electric vehicle, comprising: speed detection means capable of detecting a traveling speed of the electric vehicle, wherein when the electric vehicle is traveling and the accelerator is turned off, a preset accelerator off traveling A first braking torque calculating process for comparing the upper limit speed of the vehicle with the current running speed and calculating a first braking torque T1 necessary for setting the running speed to the upper limit speed; A second braking torque T2 which is a value;
A regenerative braking process for regeneratively braking the electric motor with a larger braking torque by comparing the first braking torque T1 obtained by the calculation with the first braking torque T1. 2. The running control method for an electric vehicle according to claim 1, wherein said upper limit speed is set by reading a running speed when an accelerator is turned off from said speed detecting means. 3. The electric vehicle regenerative control method according to claim 1, wherein the upper limit speed is set by an adjuster provided near a driver seat of the electric vehicle. 4. The first braking torque T1 is obtained by integrating the current running speed of the electric vehicle Vr, the acceleration of the electric vehicle α, the upper limit speed Vu, and the appropriate gains G1, G2, and I into integral operation parameters. , Ib is the previously calculated value of the integration operation parameter, P
Is obtained by an operation including a proportional integration operation substantially equivalent to the following equation, where P is a proportional operation parameter and Pb is a previous calculated value of the proportional operation parameter. Travel control method for electric vehicles. T1 = I + P where I = Ib + (Vr−Vu) × G1 P = Pb + α × G2, where T1 is% of the rated torque of the electric motor,
0 ≦ T1 ≦ 100 5. The regeneration of an electric vehicle according to claim 1, wherein said second braking torque T2 is set by an adjuster provided near a driver's seat of the electric vehicle. Control method. 6. A traveling electric motor supplied with electric power from a battery and driven in accordance with an operation amount of an accelerator, a traveling circuit for switching the electric motor to a regenerative braking state,
A traveling control method for an electric vehicle, comprising: speed detection means capable of detecting a traveling speed of an electric vehicle, wherein the accelerator is turned off, and regenerative braking can be performed after the traveling speed of the electric vehicle decreases. A process of setting the minimum speed of the electric vehicle that can be controlled by regenerative braking when the vehicle speed has increased, and comparing the minimum speed with the current traveling speed to determine the traveling speed as the minimum speed. A travel control method for an electric vehicle, comprising: a third braking torque calculation process for calculating a third braking torque T3; and a regenerative braking process for regeneratively braking the electric motor with the third braking torque T3. .